“Principles of cryobiology: The effect of cryopreservation on the genome of gametes and embryos”

• Julia Kopeika MD ^[1] ; MRCOG PhD ^[1]
  1. [1] Guy’s and St Thomas NHS Trust, UK
• Localización: ASEBIR, ISSN-e 1136-4424, Vol. 24, Nº. 2, 2019, 30 págs.
• Idioma: inglés
• Enlaces
  • Texto completo (pdf)
• Resumen

  • Advances in cryobiology over the last 60 years made one of the most important contributions in the improvement of overall success in assisted reproduction. Recently, the popularity of freeze all cycles due to some clinical advantages became so strong that clinicians start considering it as a default option. However, surprisingly, very little attention still has been paid to the effect of cryopreservation on genetic integrity and functionality. This paper describes in detail the physical and biochemical factors of cryopreservation that could potentially affect genomic integrity. Drawing on published literature and our own data this paper aims to summarise the evidence on genetic stability after cryopreservation of oocyte, sperm and embryos.

    Cryopreservation is a process during which a number of physical and chemical factors, such as osmotic and hydrostatic pressure, ionic intracellular content, pH and temperature, fluctuate over a wide non-physiological range which may have consequence for cellular physiology. With the remit of reproduction, the effect of cryopreservation on sperm, oocytes and embryos was studied. Some evidence suggests an increase in DNA single strand-breaks, degree of DNA condensation or fragmentation in sperm after cryopreservation. The individual and technical variables that could potentially improve the unwanted effect are described in this talk. Limited numbers of studies on human oocytes also suggest that cryopreservation may increase the rate of polyploidy, Sister Chromatid Exchange and DNA fragmentation. Different freezing regimes and type of cryoprotectants are assessed. Some animal studies show increases in DNA fragmentation rate or mitochondrial DNA variants in embryos after cryopreservation. The limited numbers of long-term follow up studies in human are reassuring but are mostly retrospective with some methodological weaknesses. Conclusions: To date there are no prospective randomised controlled trials, which assess the effect of different cryoprotectants, freezing and thawing regimes on DNA integrity in sperm, oocyte or embryos with a paucity of basic research in human embryos in this area.

    New perspectives for future research are proposed.